System.Diagnostics.Process process = new System.Diagnostics.Process();
process = System.Diagnostics.Process.Start("mspaint.exe", path);
int processId = process.Id;

AutomationElement element 

        public static AutomationElement FindWindowByProcessId(int processId)
        {
            AutomationElement targetWindow = null;
            int count = 0;
            try
            {
                Process p = Process.GetProcessById(processId);
                targetWindow = AutomationElement.FromHandle(p.MainWindowHandle);
                return targetWindow;
            }
            catch (Exception ex)
            {
                count++;
                StringBuilder sb = new StringBuilder();
                string message = sb.AppendLine(string.Format("Target　window　is　not　existing.try　#{0}", count)).ToString();
                if (count > 5)
                {
                    throw new InvalidProgramException(message, ex);
                }
                else
                {
                    return FindWindowByProcessId(processId);
                }
            }
        }

SendKeys.SendWait("{F5}");          //发送F5按键
SendKeys.SendWait("^s");       //发送 Ctrl + s 键
SendKeys.SendWait("%{F4}");      // 发送 Alt + F4 键//按键 代码 
BACKSPACE {BACKSPACE}, {BS}, 或 {BKSP} 
BREAK {BREAK} 
CAPS LOCK {CAPSLOCK} 
DEL or DELETE {DELETE} 或 {DEL} 
DOWN ARROW {DOWN} 
END {END} 
ENTER  {ENTER}或 ~ 
ESC {ESC} 
HELP {HELP} 
HOME {HOME} 
INS or INSERT {INSERT} 或 {INS} 
LEFT ARROW {LEFT} 
NUM LOCK {NUMLOCK} 
PAGE DOWN {PGDN} 
PAGE UP {PGUP} 
PRINT SCREEN {PRTSC} 
RIGHT ARROW {RIGHT} 

SendKeys.SendWait(